1 preamp out to a 2nd preamp in any harm?

I want to run a mono signal through the one preamp to a solid state 300 watt monoblock and then to the sub and from there to all the woofers in my other speakers. With the other preamp I will send the signal through a tube amp to the mids and tweeters. I like the sound of solid state in the bass and tube in the mid/tweeter range. Just don't want to destroy anything in the process.

There are a couple of unique problems with the current set up. The Sub has a rythmic plate amp that produces a hum in the system when connected via RCA, the hum disappears when connected via speaker inputs. The mono signal will be generated via y output from the preamp going to the monoblock. The monoblock will connect via speaker wires to the crossover system in the rythmic plate amp with one feed going to the sub and one feed going to the woofers. If this produces distortion or an echo effect I may just run a mono feed to the back speakers from the sub. Again I have know idea what this will sound like I just do not want to destroy anything finding out.

Elizabeth you were spot on and this does sound great. I only went from second preamp to sub to rear speakers making them mono and it did everything I needed. I did not mess with crossovers in each speaker to obtain the complete seperation of woofers, to much work at this time and I like the results of what I did. I can fine no deterioration in sound and the rears set at a lower volume then the front actually help with the sound stage versus the two sets in stereo which in my large room and old ears had a poor front to back seperation. Thanks for the encouragement. Bass is now extremely tight a sound I have always preferred.